Rails 3 and Heroku: automatically "rake db:migrate" on push?

I have a slight annoyance with my heroku push/deploy process, which otherwise has been a joy to discover and use.

If i add a new migration to my app, the only way i can get it up onto the heroku server is to do a push to the heroku remote. This uploads it and restarts the app. But it doesn't run the migration, so i have to do

heroku rake db:migrate --app myapp

, then

heroku restart --app myapp

. In the meantime, the app is broken because it hasn't run the migrations and the code is referring to fields/tables etc in the migration.

There must be a way to change the deployment process to run the

rake db:migrate

automatically as part of the deploy process but i can't work it out.

Is it something i set in a heroku cpanel? Is it an option i pass to heroku from the command line? Is it a git hook? Can anyone set me straight? thanks, max